Multiple pusher liquid color pump

ABSTRACT

A liquid color pumping includes a housing, a plurality of pushers within the housing, a deformable tube for transporting liquid color from the supply thereof to where the liquid color will be used with the tube being positionably removable in the housing at a location at which of the pushers when displaced squeeze the tube positioning of the pushers resulting in the pushers serially contacting the tube when displaced and the controller repeated actuating the pushers in sequence to draw liquid color into the pumping zone and then to force liquid color out of the pumping zone through the tube at increased pressure.

CROSS REFERENCE TO RELATED APPLICATION

This patent application discloses subject matter in common with U.S. patent application Ser. No. ______ entitled “Liquid Color Gravimetric Metering Apparatus and Methods”, filed concurrently herewith in the name of Stephen B. Maguire.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to processing of plastic resin material for fabrication into finished plastic parts and more particularly to methods and apparatus for pumping liquid color material used to impart a desired color to the finished plastic parts.

2. Description of the Prior Art

Color is imparted to finished plastic parts by adding a coloring agent, either liquid color material or solid color pellets, to plastic resin material as it is being fabricated into finished plastic parts. The liquid color or the colored pellets control the color of the finished plastic parts. Depending on whether liquid color or solid colored pellets is used, the position at which the coloring agent is added to the plastic resin material during the part fabrication process may change.

Pumps for liquid color are known. Liquid color diaphragm pumping apparatus is disclosed in pending U.S. patent application Ser. No. 10/066,338, published as United States patent publication 2003-0142580, and in pending U.S. patent application Ser. No. 10/856,422, published as United States patent publication 2005-0052945.

Additionally, peristaltic pumps are commonly used for pumping liquid color because all of the liquid color remains in the peristaltic pump tubing, at all times. As a result, when changing colors there is no contamination of the liquid color and no clean up required. When using a peristaltic pump, the only thing required to change colors is to change the tube in the peristaltic pump. However, peristaltic pumps, with these advantages, tend to be unreliable and are expensive.

SUMMARY OF THE INVENTION

The multiple pusher liquid color pump of this invention in its preferred embodiment uses three pneumatic cylinder driven pushers and three solenoids to operate those pneumatic cylinders in a carefully selected sequence of on and off pulses. When operating the pump, a deformable tube is placed below the pushers. The pushers are desirably positioned side by side in a housing and are attached to the ends of pusher rods connected to the pneumatic cylinders. These desirably plastic pushers periodically press on the tube, which is in front of the pushers, thereby squeezing and compressing the tube against a preferably flat surface.

The three pushers are preferably aligned and adjacent one to another. As a result, in the course of one sequence of pusher operations, the first and second pushers serve as check valves, compressing the tube and thereby shutting off flow through the tube when either of these pushers is activated. Then, when activated and advanced, the center pusher squeezes the tube to displace liquid color forward. When retracted, the center pusher permits the tube to relax. This serves to suck in liquid color from the liquid color supply, for subsequent additional pumping. The sequence is repeated, rapidly, to provide the desired flow of liquid color material.

This pump has many of the advantages of peristaltic pumps, but is simpler and costs considerably less. This pump does not include a drive motor, has no bearings and does not include any DC drive circuitry. The solenoids are preferably driven by simple on/off signals preferably from a simple, low cost, computerized control. Variable output of the pump is achieved by regulating the timing of the pulse sequences, i.e., performing the sequences faster or slower. Like a peristaltic pump, use of different diameter tubes produces different pump ranges for output of liquid color.

Accordingly, in one of its aspects this invention provides a pump for liquid color used in fabrication of plastic parts by molding or extrusion, where the pump preferably includes a housing, pushers, desirably three, within the housing, with the pushers preferably being positioned side by side respecting one another, a compressible tube for transporting liquid color from a supply thereof to where the liquid color is to be used, with the tube preferably being removably insertable into the housing to a position at which each of the pushers, when displaced, squeezes the tube against structure connected to or forming a part of the housing, with the side by side positioning of the pushers resulting in the pushers, upon appropriate actuation, contacting and squeezing the tube in a desired, preselected sequence of operations.

In this aspect, the invention preferably further includes a controller for repeatedly actuating the pushers in sequence whereby a first pusher is preferably displaced to squeeze the tube closed while the second pusher and the third pusher are not displaced, thereby permitting liquid color to flow through the tube from the supply to a first position of tube closure, preferably then the second pusher is preferably displaced to squeeze the tube closed and trap liquid color in the tube between the first position of tube closure and a second position of tube closure, and preferably then the first pusher is preferably permitted to return to its undisplaced position thereby permitting liquid color to flow through the tube past the first position of tube closure and preferably a third pusher is displaced preferably to squeeze the tube and thereby force at least a portion of the trapped liquid color through the tube past the first position of tube closure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation of a multiple pusher liquid color pump of this invention, for use in practicing the method aspects of this invention.

FIG. 2 is a broken front elevation of the lower portion of the pump illustrated in FIG. 1, with a liquid color delivery tube removed from the pump housing and shown outside the pump housing.

FIGS. 3A through 3F are schematic depictions of three pushers, illustrated in FIGS. 1 and 2, forming portions of the pump.

FIG. 3A depicts the pushers at an initial position at which all three pushers are retracted and are ready to begin one cycle of pusher movement for pumping liquid color.

FIG. 3B depicts the pushers at positions at which a first pusher has advanced to squeeze the liquid color supply tube closed, while the second and third pushers have not been displaced, thereby permitting liquid color to flow through the squeezable liquid color supply tube from the supply to a first position of tube closure.

FIG. 3C depicts the pushers at positions with a second pusher having additionally been displaced to squeeze the liquid color supply tube closed and thereby trap liquid color in the tube between the first position of tube closure defined by the first pusher and a second position of tube closure defined by the second pusher.

FIG. 3D depicts the pushers at positions at which the first pusher has retracted, the second pusher remains in place to keep the liquid color supply tube closed at the second position of tube closure, and a third, center pusher has been displaced to squeeze the liquid color supply tube and thereby forcedly squeeze some of the trapped liquid color through the tube past the first position of tube closure thereby supplying liquid color to a plastic resin processing machine.

FIG. 3E depicts the pushers at positions at which the second pusher remains displaced to continue squeezing the liquid color supply tube closed while the third pusher has completed travel towards the liquid color supply tube thereby completing squeezing of the liquid color supply tube and forcing substantially all of the liquid color which had been trapped within the liquid color supply tube downstream of the seal position of tube closure out of the liquid color tube towards a plastic resin processing machine for consumption of the liquid color.

FIG. 3F depicts the pushers at positions at which the second and third pushers have retracted, the first pusher has advanced to squeeze the liquid color supply tube closed at the first position of tube closure thereby permitting liquid color to flow into the tube from the supply to the first position of tube closure whereupon the cycle of pusher movement for supplying liquid color through the liquid color supply tube to a plastic resin process machine may repeat.

DESCRIPTION OF THE PREFERRED EMBODIMENTS AND BEST MODE KNOWN FOR PRACTICE OF THE INVENTION

Referring to FIG. 1 where triple pusher pump 16 is illustrated with the front panel of the pump housing removed in order that the interior components of triple pusher pump 16 may be viewed, pusher pump 16 includes three pushers, designated 28, 30, 32 respectively. Pushers 28, 30, 32 act against and squeeze liquid color supply line 22 in an ordered sequence thereby to control flow of liquid color through supply line 22 and to pump liquid color to a plastic resin process machine such as an extruder or an injection molding press via liquid color supply line 22. Each of first, second and third pushers 28, 30, 32 is connected to and actuated by a piston-cylinder combination, where first, second and third piston-cylinder combinations have been designated 34, 36, 38 respectively as being associated with first, second and third pushers 28, 30 and 32.

First piston-cylinder combination 34 has been shown with the exterior of the cylinder portion of the combination cut away to reveal the inner workings of piston-cylinder combination 34. As visible in FIG. 1, piston-cylinder combination 34 includes a cylinder designated 56 and a piston 58, where piston 58 is in a form of a relatively flat plate.

Piston cylinder combination 34 further includes a piston return spring 60, which is preferably of spiral configuration and slidably contacts the curved interior of cylinder 56, serving to return piston 58 to a vertically extreme upwards position when pressurized air is not furnished to piston-cylinder combination 34.

A first solenoid designated generally 40 actuates a first air valve designated generally 46 to supply compressed air via a line 61 to first piston-cylinder combination 34, thereby to push piston 58 downwardly. Fixed to piston 58 is a connecting rod 62 to which first pusher 28 is affixed, at the end of connecting rod 62 remote from piston 58. First, second and third piston-cylinder combinations 34, 36, 38 rest on plate 66 and are retained in position thereon by suitable nut and bushing combinations, one of which is designated 64 in FIG. 1. Connecting rod 62 passes slidably within nut-bushing combination 64 as connecting rod 62 reciprocates responsively to downward force resulting when air is applied to the upper side of piston 58 and, once that air pressure is relaxed, when return spring 60 urges piston 58 upwardly into the position in the position illustrated in FIG. 1.

In comparing FIG. 1 with FIG. 2 it is evident that liquid color supply line 22 may be removed from housing 68 in which pump 16 is enclosed. Such positioning of liquid color supply line 22 outside of housing 68 is illustrated in FIG. 2.

A controller, not illustrated, connects to solenoids 40 via lines 54 and is programmable so as to permit any desired sequence of operation of piston-cylinder combinations 34, 36, 38 thereby to permit any desired sequence of squeezing or unsqueezing of liquid color supply line 22 when positioned within housing 68 in the general manner illustrated in FIG. 1.

First and third pushers 28, 32 are configured outer peripheries that are curved, and would appear as cylinders if viewed from the side in FIGS. 1 and 2, facing towards liquid color supply line 22. These curved outer peripheries are designated 70 in FIGS. 1 and 2. The curved outer peripheries 70 of pushers 28, 32 facilitates pushers 28 and 32 operating as off-on valves as respecting flow of liquid color through liquid color supply line 22. Specifically, curved peripheries 70 permit pushers 28, 32 to act as off-on valves defining first and second positions of tube closure, with a first position of tube closure being directly beneath pusher 28 and the second position of tube closure being directly beneath pusher 32. The curvature of surfaces 70 contacting liquid color supply tube 22 when pushers 28 and 32 are positioned against tube 22 and have squeezed tube 22 closed means tube 22 is closed only over a very short length, immediately beneath pushers 28 and 32, when either of those pushers are actuated by their associated piston-cylinder combination 34 or 38.

Contrasting, third pusher 30 has a surface 72 facing liquid color supply tube 22 that is flat. Surface 72, being flat, results in liquid color within the portion of tube 22 directly beneath pusher 30 and along the entire length of surface 72 running parallel to liquid color supply line 22, being pushed out of liquid color supply line 22 when third pusher 30 is actuated by associated piston-cylinder combination 36 and pusher 30 squeezes liquid color supply line 22 completely closed, thereby forcing all liquid color material within liquid color supply line 22 beneath the projected area of pusher 30 towards the outlet of liquid color supply line in the direction indicated by arrow B in FIG. 1.

Actuation of a given solenoid such as solenoid 40 by the controller, via a signal sent to solenoid 40 through line 54, opens valve 46 thereby allowing pressurized air from a remote source, not illustrated in the drawings, which is furnished to valve 16 via an air line not shown in the drawings, to be applied to the upper surface of piston 58 forcing piston 58 downwardly in FIG. 1 and thereby actuating, for example, pusher 28 and forcing pusher 28 against liquid color supply line 22, thereby to close liquid color supply line 22 at a position at first tube closure.

FIGS. 3A through 3F depict one desired and preferred sequence of operation of pushers 28, 32, 30 to pump liquid color through liquid color supply line 22.

In FIG. 3A pushers 28, 30, 32 are all depicted at an initial position, at which all three pushers 28, 32, 30 are retracted and are ready to begin one cycle of pusher movement for pumping liquid color through liquid color supply line 22. Arrow A denotes that liquid color is entering liquid color supply line 22 and Arrow B denotes liquid color exiting liquid color supply line 22 after passing the position of pushers 28, 32, 30.

Referring to FIG. 3B, first pusher 28 has advanced to squeeze liquid color supply line 22 closed at a position to first tube closure while second pusher 32 and third pusher 30 have not been displaced. Accordingly, liquid color continues to flow into liquid color supply line 22 from a supply of liquid color as indicated by Arrow A, but the liquid color cannot flow past the first position of tube closure defined by the intersection of first pusher 28 with liquid color supply line 22, since first pusher 28 has squeezed liquid color supply line 22 closed.

Next, as illustrated in FIG. 3C, second pusher 32 has been displaced to squeeze liquid color supply line 22 closed thereby to define a position of second tube closure, and thereby has trapped liquid color in the segment of liquid color supply line 22 between the first and second positions of tube closure as defined by first pusher 28 and second pusher 32 having squeezed liquid color supply line 22 closed at the positions shown. Such squeezing and resulting closure of liquid color supply line 22 traps a portion of liquid color between the two positions of liquid color supply line closure, as illustrated in FIG. 3C, between pushers 28 and 32.

Next, first pusher 28 is retracted by release of the air pressure through deactuation of the associated solenoid 40 and action of return spring 60 pushing piston 58 in cylinder 56 upwardly, thereby raising first pusher 28 away from and out of contact with liquid color supply line 22, as illustrated in FIG. 3D. At the same time, third pusher 30 is actuated, begins to travel downwardly, and encounters liquid color supply line 22 as illustrated in FIG. 3D. This encounter begins to compress liquid color supply line 22 as illustrated in FIG. 3D thereby beginning to push liquid color out of that segment of liquid color supply line 22 in the direction indicated by Arrow B in FIG. 3D. This liquid color can only move in the direction of Arrow B in FIG. 3D due to the continued presence of second pusher 32 in the position illustrated in FIG. 3D whereby second pusher 32 has closed liquid color supply line 22 at the position of second tube closure. Therefore, there is only one direction that liquid color can travel in response to the tube being squeezed by third pusher 30.

As depicted in FIG. 3E, third pusher 30 continues its downward travel, continuing to squeeze liquid color supply line 22 more and more closed, thereby continuing to force liquid color that was within liquid color supply line 22 below the umbrella of third pusher 30, out of liquid color supply line 22, in the direction indicated by Arrow B in FIG. 3E. As was the case illustrated in FIG. 3D, continued presence of second pusher 32 squeezing liquid color supply line 22 closed as illustrated in FIG. 3E results in liquid color within liquid color supply line 22 being able to move only in a single direction, indicated in Arrow B in FIG. 3E.

Once third pusher 30 has completed squeezing the liquid color that is within tube 22 below the umbrella of pusher 30, first pusher 28 is actuated thereby closing liquid color supply tube 22 at a position of first tube closure, where first pusher 28 has squeezed liquid color supply tube closed, thereby preventing passage thereby of any liquid color. Second pusher 32 and third pusher 30 have been retracted by deactuation of their associated solenoids, which are not numbered in FIG. 1, with the result that second and third pushers 30, 32 have retracted to a position above and out of contact with liquid color supply line 22. As a result, liquid color again fills the portion of liquid color supply line 22 up to the position of first tube closure defined by pusher 28, with the liquid color coming from the supply in the direction indicated by Arrow A in FIG. 3F. From this position the pumping cycle may repeat. Note that the orientation and positions of first, second and third pushers 28, 32, 30 is identical in FIGS. 3F and 3B.

The controller preferably adjusts the speed of pump 16 so that the desired amount of liquid color preferably is always supplied by pump 16 at the rate needed for a given material recipe. Hence, pump 16 is preferably controlled to run faster or slower in order to maintain a desired rate of liquid color use. 

1. A pump for liquid color, comprising: a) a housing; b) a plurality of pushers within the housing; c) a deformable tube for transporting liquid color from a supply thereof to where the liquid color will be used; d) the tube being insertable into the housing and positionable to a location therein at which at least one of each of the pushers when displaced squeezes the tube against a stop; and e) a controller for actuating the pushers in sequence whereby the pusher which upon displacement squeezes the tube against a stop thereby forces at least a portion of liquid color through the tube towards the position at which the liquid color will be used.
 2. The pump of claim 2 where the controller repeatedly actuates the pushers.
 3. A pump for liquid color, comprising: a) a housing; b) a pusher within the housing; c) a deformable tube for transporting liquid color from a supply thereof to where the liquid color will be used; d) the tube being removably positionable within the housing to a location at which the pusher when displaced squeezes the tube; and e) a controller for actuating the pusher whereby upon pusher displacement squeezing the tube at least a portion of the liquid color is forced through the tube and out of the pump.
 4. The pump of claim 4 in which the controller repeatedly actuates the pusher.
 5. A pump for liquid color, comprising: a) a housing; b) three pushers within the housing, positioned side by side respecting one another; c) a compressible tube for transporting liquid color from a supply thereof to where the liquid color will be used; d) the tube being insertable into the housing to a position at which each of the pushers when displaced squeeze the tube against the housing interior, with the side by side positioning of the pushers resulting in the pushers serially contacting the tube when displaced; and e) a controller for repeatedly actuating the pushers in sequence whereby a first pusher is displaced to squeeze the tube closed while a second and a third pusher are not displaced, thereby permitting liquid color to flow through the tube from the supply to a first position of tube closure, then the second pusher is displaced to squeeze the tube closed and trap liquid color in the tube between the first position of tube closure and a second position of tube closure, then the first pusher is permitted to return to its undisplaced position thereby permitting liquid color to flow through the tube past the first position of tube closure and the third pusher is displaced to squeeze the tube and thereby force at least a portion of the trapped liquid color through the tube past the first position of tube closure.
 6. A pump for liquid color, comprising: a) a housing; b) a plurality of pushers within the housing; and c) a controller for actuating the pushers in sequence whereby a pusher upon displacement squeezes a deformable tube thereby forcing at least a portion of liquid color through the tube towards a location at which the liquid color will be used.
 7. A method for pumping liquid color, comprising repeatedly actuating three pushers, positioned side by side respecting one another, in sequence whereby a first pusher is displaced to squeeze a compressible tube, for transporting liquid color from a supply thereof to where the liquid color will be used, into a closed disposition while a second and a third pusher are not displaced, thereby permitting liquid color to flow through the tube from the supply to a first position of tube closure, then the second pusher is displaced to squeeze the tube closed and trap liquid color in the tube between the first position of tube closure and a second position of tube closure, then the first pusher is permitted to return to its undisplaced position thereby permitting liquid color to flow through the tube past the first position of tube closure and the third pusher is displaced to squeeze the tube and thereby force at least a portion of the trapped liquid color through the tube past the first position of tube closure.
 8. The method of claim 7 further comprising removably positioning the compressible tube within a pusher housing to a location at which a displaced pusher squeezes the tube.
 9. A method for pumping liquid color, comprising: a) repeatedly actuating three pushers, positioned side by side respecting one another, in sequence by, i) displacing a first pusher to squeeze a compressible tube, for transporting liquid color from a supply thereof to where the liquid color will be used, into a closed disposition, and ii) retaining a second and a third pusher from displacement, iii) thereby permitting liquid color to flow through the tube from the supply to a first position of tube closure, iv) displacing the second pusher to squeeze the tube closed and trap liquid color in the tube between the first position of tube closure and a second position of tube closure; and v) returning the first pusher to its undisplaced position; vi) thereby permitting liquid color to flow through the tube past the first position of tube closure; and vii) displacing the third pusher to squeeze the tube and thereby force at least a portion of the trapped liquid color through the tube past the first position of tube closure.
 10. The method of claim 7 further comprising removably positioning the compressible tube within a pusher housing to a location at which a displaced pusher squeezes the tube. 